ulimit

On Thu, 08 Nov 2007, in the Usenet newsgroup comp.os.linux.security, in article
<1194494735.248243.325540 RemoveThis @d55g2000hsg.googlegroups.com>, Steven Borrelli wrote:

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>How can I (being root) prevent other users from changing their ulimit?

You can't. They can _reduce_ their limits, or increase them up to
the limits you set, but it's not easy to prevent anyone from changing
them below those maximum limits.

>I know this is possible in UNIX, but I'm not sure about Linux (i.e.
>Slackware, SUSE). By the way, how would I do it in UNIX? (i.e.
>Solaris, Darwin, or FreeBSD)

It's a _shell_ function, not an O/S. You're probably running a Bourne
type shell (sh, bash, ksh, or similar), and for that the built-in
command is 'ulimit'. For a 'c' type shell (csh, tcsh, and similar),
the command is 'limit'.

Limits are set in a login shell - so if you are using a text based
login and a Bourne shell, use /etc/profile. If using a 'csh' shell,
use ~/.login in the users home directory. If using a 'tcsh' shell,
see the man page, as things vary as a function of how the shell is
compiled. For a _GUI_ login (runlevel 5 in an Linux Standard Base
compliant distribution)[1], you need to look at the man page for the
display manager used (gdm, kdm, wdm, xdm, etc.) as they usually
do NOT use a shell as the place to set things - .xinitrc, .xsession,
or similar - often in the user's home directory. For those files
that set the limits but are located _in_ the user's home directory,
you need to change ownership of that/those files to root:root, and
set the 'sticky bit' on the directory itself (chmod 1750 /home/mumble)
so that only the file _owner_ can delete the file.

Bottom line - see the man page for the shell used, and read the
sections about limits and shell invocation.

Old guy

[1] Mandriva 2008 is an exception. The GUI login shell scripts source
~/.bash_profile - which isn't much good in a 'csh' environment, but is
a start.

Steven Borrelli wrote:
> How can I (being root) prevent other users from changing their ulimit?
> I know this is possible in UNIX, but I'm not sure about Linux (i.e.
> Slackware, SUSE). By the way, how would I do it in UNIX? (i.e.
> Solaris, Darwin, or FreeBSD)

For Linux
man limits.conf

limits.conf lives in /etc/security usually.
It applies (or could apply, depending on configuration) to any user.
It's not dependent on shell. You can use the shell ulimit command to
change soft limits, like a previous poster said, but hard limits are
absolute maximums.